1. Field of the Invention
The present general inventive concept relates to a two-panel type projection system and a projection method thereof, and more particularly, to a two-panel type projection system adapted to express a high brightness picture, and a projection method thereof.
2. Description of the Related Art
Recently, demands on a large screen display are increased due to a normalization of High Definition (HD) broadcasting using a satellite and a ground wave and a popularization of a home theater using a DVD player. Since a projection television replaces a conventional Cathode Ray Tube (CRT) television due to its advantage of manufacturing the large screen display at lowered manufacturing costs, a projector providing the larger screen display than the projection television is being increasingly demanded.
A projection system is a main component of the projection television or the projector. A three-panel type projection system has been used with three-panels respectively corresponding to Red/Green/Blue light components of a white light. However, the three-panel type projection system has a disadvantage of high manufacturing costs. Accordingly, a single panel type projection system has been developed to have a single panel to modulate all three light components, thereby reducing the manufacturing costs.
The single panel type projection system is advantageous of the manufacturing costs compared to the three-panel type projection system. However, the single panel type projection system has a drawback in that since the Red/Green/Blue light components are sequentially sent to one panel, the single panel type projection system has at most ⅓ of a light efficiency of the three-panel type projection system, thereby reducing a brightness, and in that a lamp is required to have a large capacity as a light source to generate light having the same brightness as the three-panel type projection system, thereby decreasing a life span of the lamp according to an increased capacity of the lamp.
Accordingly, a conventional two-panel type projection system of FIG. 2 is popularized due to its lowered manufacturing costs compared to the three-panel type projection system, and its high light efficiency compared to the single panel type projection system.
FIG. 2 is a view illustrating a schematic construction of a conventional two-panel type projection system.
As shown in FIG. 2, the two-panel type projection system includes a polarization light source 30, a color selector 32, a polarization conversion device 34, a polarization beam splitter 36, a first panel 38, a second panel 40, and a projection lens 28.
The polarization light source 30 outputs a single polarization component of a white light, and generally outputs an S-polarized light beam. The polarization light source 30 includes a lamp for irradiating a high-brightness white light, a Fly Eye Lens (FEL) for receiving the irradiated light to convert the received light into a parallel light, and a polarization conversion unit for receiving the parallel light from the FEL to convert the received parallel light into a specific polarization component.
The color selector 32 continuously transmits one of Red/Green/Blue light components, and alternatively transmits remaining two light components. For example, the color selector 32 repeats to transmit Red and Green light components (R+G) for a first time duration, and transmit Red and Blue light components (R+B) for a second time duration. The color selector 32 can be a rotatable dichroic wheel. The light component continuously transmitting the color selector 32 is differently determined depending on the lamp used in the polarization light source 30. For example, an Ultra-High Pressure (UHP) hydrargyrum lamp needs to supply more Green or Blue light component than Red light component to provide the white balance, due to an insufficient light amount of the Red light component, compared to the Green and Blue light components. In this case, the color selector 32 is configured to allow the Red light component outputted from the polarization light source 30 to continuously transmit the light to the color selector 32.
The polarization conversion device 34 converts the polarization of a specific light component. Here, an S-polarization of the Red light component is converted into a P-polarization.
The polarization beam splitter 36 has an interface having a coated dichroic film to transmit one polarization light component and reflect another polarization light component. Generally, the S-polarized light component is reflected and the P-polarized light component is transmitted. In this case, the P-polarized Red light component using the polarization conversion device 34 is incident on the second panel 40, and the S-polarized Green and Blue light components are sequentially incident on the first panel 38.
If the Green light component and the Blue light component are sequentially incident, the first panel 38 is driven by a signal unit (not shown) to sequentially modulate and reflect the Green light component and modulate and reflect the Blue light component. At this time, the polarizations of the reflected light components are converted into opposite polarizations of the incident light components. In this example, the S-polarization of the Green and Blue light components is converted into the P-polarization.
If the Red light component is incident, the second panel 40 is driven by the signal unit (not shown) to modulate and reflect the Red light component. At this time, the polarization of the reflected light component is converted into the opposite polarization of the incident light component. In this example, the P-polarization of the Red light component is converted into the S-polarization.
The P-polarized Green and Blue light components are transmitted through the coated interface of the polarization beam splitter 36 to be incident on the projection lens 28. The S-polarized Red light component is reflected from the coated interface of the polarization beam splitter 36 to be incident on the projection lens 28. The projection lens 28 magnifies and projects the incident Red/Green/Blue light components to produce a color image.
For example, the conventional two-panel type projection system has a dedicate panel for one color, which is selected depending on a lamp property, to continuously express one color, and the other panel to express remaining two colors in a time division way. In this case, a color temperature can be controlled according to a time division ratio of two colors expressed in the time division way. In this example, the color temperature is controlled using a time division ratio of the Green and Blue light components.
Since the conventional two-panel type projection system continuously expresses one color by using the dedicate panel, a time ratio of the remaining two colors expressed using the other panel should be varied to change the color temperature. Accordingly, the conventional two-panel type projection system has a drawback in that the color distribution is not free. Further, the conventional two-panel type projection system has a drawback in that the brightness is totally lowered since the brightnesses of the remaining colors should be lowered adaptively to the color having the lowest brightness so as to maintain the white balance at the time of controlling the color temperature.